Hi Roger - I use the method of figure 7.66 "Series TC." This is simple with a nanoVNA, or any VNA. For this particular coil, I found an old CD 470 pF silver mica cap and used that along with a 30 pF NP0 in parallel. I have kept a piece of PCB with coax connectors and an exposed microstrip line of an inch or so to solder coils and caps to. I use Eq 7.4 noting that A is the attenuation and thus a positive number. Bob
